In a millimeter wave area, single-connection antenna arrays are of interest, meaning that each antenna is only equipped with one phase shifter and analog antennas are separated into several groups, each group is combined independently into separated RF chains, instead of full-connection antenna arrays, that each RF chain has full access to all analog antennas and each analog antenna are connected with multiple phase shifters.
A typical implementation for analog beamforming uses an exhaustive search method to select a beamforming vector from a given codebook. Such a search method, however, does not guarantee optimality.